From 0bc04e327c54db788b0a7093879e3c4e51301356 Mon Sep 17 00:00:00 2001 From: James Date: Sun, 15 Nov 2020 20:34:16 -0600 Subject: [PATCH] Update E0744 about control flow in `const` contexts to reflect the current status of `const fn`. This is a squash of these commits: - Update E0744 about control flow in `const` contexts to reflect current status of `const fn`. - E0744 isn't just about `for` loops or control flow - Fix formatting on E0744 cause my editor decided to not copy it well - Improve wording - Fix a markdown formatting error - Fix E0744's description as I interpreted some code wrong - Fix a minor wording issue again - Add a few more links to blocking issues - Improve links to tracking issues --- .../src/error_codes/E0744.md | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/compiler/rustc_error_codes/src/error_codes/E0744.md b/compiler/rustc_error_codes/src/error_codes/E0744.md index 14cff3613e023..45804ab266e28 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0744.md +++ b/compiler/rustc_error_codes/src/error_codes/E0744.md @@ -1,4 +1,4 @@ -A control-flow expression was used inside a const context. +An unsupported expression was used inside a const context. Erroneous code example: @@ -12,12 +12,15 @@ const _: i32 = { }; ``` -At the moment, `if` and `match`, as well as the looping constructs `for`, -`while`, and `loop`, are forbidden inside a `const`, `static`, or `const fn`. +At the moment, `for` loops, `.await`, and the `Try` operator (`?`) are forbidden +inside a `const`, `static`, or `const fn`. -This will be allowed at some point in the future, but the implementation is not -yet complete. See the tracking issue for [conditionals] or [loops] in a const -context for the current status. +This may be allowed at some point in the future, but the implementation is not +yet complete. See the tracking issues for [`async`] and [`?`] in `const fn`, and +(to support `for` loops in `const fn`) the tracking issues for [`impl const +Trait for Ty`] and [`&mut T`] in `const fn`. -[conditionals]: https://github.com/rust-lang/rust/issues/49146 -[loops]: https://github.com/rust-lang/rust/issues/52000 +[`async`]: https://github.com/rust-lang/rust/issues/69431 +[`?`]: https://github.com/rust-lang/rust/issues/74935 +[`impl const Trait for Ty`]: https://github.com/rust-lang/rust/issues/67792 +[`&mut T`]: https://github.com/rust-lang/rust/issues/57349